Hydrazine



D. W. RYKER Oct. 30, 1956 HYDRAZINE Filed June 24, 1955 3o PERCENTAGEOF. GUANIDINE NITRATE INVENTOR. gem w. RYKER AGENT HYDRAZINE Don W.Ryker, Alton, Ill., assignor to Olin Mathieson Chemical Corporation, acorporation of Virginia Application June 24, 1953, Serial No. 363,814

2 Claims. (Cl. 52.5

This invention relates generally to hydrazine and to water solutionsthereof and more particularly to hydrazine compositions havingadvantageous freezing points and to a method for making them.

It has been proposed heretofore to use hydrazine or compositions ofhydrazine hydrate or hydrazine and water as a fuel in internalcombustion engines, jet-propelled heavier-than-air craft, and as apropellant in rockets and ammunition cartridges. Hydrazine has proven tobe one of the most efficient compounds available for these purposes andhas three of the four primary requisites of an ideal fuel, namely, (1)high density, (2) low viscosity, and (3) low molecular weight combustionproducts. Hydrazine is not entirely suitable for the purpose, however,because its freezing point is about 2 C. and will thus solidify at highaltitudes or under some weather conditions and become ineffective as afuel.

It is therefore an object of this invention to provide a hydrazinecomposition adapted for use in rockets, jet propelled devices, internalcombustion engines, ammunition cartridges and similar devices which isdevoid of the foregoing disadvantages of prior art hydrazinecompositions. It is another object of this invention to provide ahydrazine composition having a freezing point below that of anhydroushydrazine. A further object of the invention is to provide a hydrazinecomposition especially well suited for use as a fuel at high altitudesand in the colder regions of the world. A still further object of theinvention is to provide a method for making hydrazine compositionshaving an advantageous freezing point.

Other objects and advantages will be apparent from the followingdescription and accompanying drawing which illustrates the freezingpoint curve of hydrazineguanidine nitrate mixtures with the weightpercent of guanidine nitrate as abscissa and the freezing pointtemperatures in C. as the ordinate.

It has been found in accordance with this invention that the foregoingobjects as well as others can be achieved by providing hydrazinecompositions containing guanidine nitrate. The hydrazine composition maybe formed from aqueous or anhydrous hydrazine. By hydrazine as used inthe appended claims is meant, therefore, aqueous solutions of hydrazineas well as anhydrous hydrazine. Guanidine nitrate is a solid andcrystals thereof can be added to the hydrazine composition. Whereasguanidine nitrate has been found advantageous for the purpose, somehomologous compounds including nitroguanidine and triaminoguanidinenitrate have been found unsuitable for the purpose.

It is, of course, well known that the freezing or melting point of acompound is in general lowered by the inclusion therein of an impurityor other compound. In fact, the amount of lowering of the freezing pointto be expected by a given amount of another compound may be calculatedin accordance with the equation 2,768,888 Patented Oct. 30, 1956 whichis derived from the Clapeyron equation and Raoults law where n=molefraction of solute, L =heat of fusion of the solvent, R=gas constant,T=freezing point of the solution or mixture, and Tm=melting point of thesolvent. Referring to the drawing the broken line A, indicates thefreezing point to be expected by the addition to hydrazine of guanidinenitrate. The points for the curve A, were calculated from the foregoingequation.

It has been discovered, however, that mixtures of hydrazine andguanidine nitrate do not follow Raoults law and that the freezing pointof a mixture thereof can not be predicted from the foregoing equation.On the contrary, as it will be noted from the solid line curve of thedrawing which represents the freezing point curve of hydrazine andguanidine nitrate mixtures the freezing points are unexpectedly lowerthan would be predicted. For example, it is possible to lower thefreezing point of hydrazine from about 2 C. to about 32 C. by addingabout 27.5 percent by weight guanidine nitrate. As shown by the curve ofthe drawing, additions of larger percentages of guanidine nitrateindicate that this concentration is the eutectic point. Actually, asindicated, larger quantities of up to about 35 percent guanidinenitrate, can be added and a depression of the freezing point obtained,but obviously utilization of amounts up to that required to reach theeutectic point are preferred, although compositions are contemplatedwhich contain any amount of the freezing depressant and have a freezingpoint below that of hydrazine.

Although some water does not deleteriously effect the ignitability ofthe hydrazine composition amounts of water greater than about one partwater per part of hydrazine are not particularly desirable in fuels orpropellants. Substantially anhydrous hydrazine, say about percent topercent hydrazine is preferred for such combustion purposes.

Because of the solubility or miscibility of guanidine nitrate, nodifiiculty is encountered in formulating improved hydrazine compositionsin accordance with this invention. They may be readily prepared bymerely mixing the constituents together in such proportions or amountsas set forth hereinbefore depending upon the freezing point desired. Theonly precautions necessary are those incident to handling hydrazine,which precautions are known to the art. It has been found that thecompositions provided by the invention are stable under a variety ofconditions so mixing just prior to use is not a requisite.

As an example, as illustrated in the accompanying drawing, a lowfreezing point composition suitable for a fuel may be prepared inaccordance with one embodiment of this invention by mixing about 27.5parts guanidine nitrate with about 72.5 parts of hydrazine whosecomposition is about 95 percent hydrazine and about 5 percent water. Thecrystals of guanidine nitrate can be conveniently poured into thehydrazine from any suitable container therefor such as the one in whichit is weighed. The mixing may be accomplished at room temperature and,when the guanidine nitrate has dissolved a hydrazine composition isobtained having a freezing point of about 33 C. Compositions havingfreezing points anywhere within the range of -33 C. to the freezingpoint of hydrazine may be obtained in accordance with a process similarto that just described except the quantity of freezing point depressantis varied as indicated by the curve shown in the drawing.

The freezing point depressant of this invention, in general, continuesto exhibit the faculty of depressing the freezing point of hydrazinecompositions even when com patible compounds other than hydrazine andwater are included therein. Hydrazine compositions having hy- 3 drazineas the major constituent thereof and having the freezing pointdepressant incorporated therein and also containing the usual additivesto fuels such as, for example, coloring agents, accelerators,stabilizers, retardants, or other modifiers or hydrazine compositionsincorporated in other fuels are therefore contemplated by thisinvention.

While specific compositions have been described in detail in theforegoing, various changes will occur to and can be made therein bythose skilled in the art without departing from the spirit and scope ofthis invention and the invention is not limited to such details exceptas set forth in the appended claims. 7

Having thus described the invention, what is claimed and desired tosecure by Letters Patent is:

1. As a new composition of matter, a substantially anhydrous mixture ofhydrazine and guanidine nitrate 4 j in the ratio of about 72.5 partshydrazine and about 27 .5 parts guanidine nitrate.

2. A method for lowering the freezing point of substantially anhydroushydrazine which comprises dissolv-. ing therein about one part guanidinenitrate in about three parts hydrazine. 7

References Cited in the file of this patent V UNITED STATES PATENTS 102,159,234 I Taylor May 23, 1939 2,521,026 Solomon Sept. 5', 19502,555,333 Grand et a l. June 5, 1951 OTHER REFERENCES 15 Klein: SAEJournal, December 1947, p. 25.

1. AS A NEW COMPOSITION OF MATTER, A SUBSTANTIALLY ANHYDROUS MIXTURE OFHYDRAZINE AND GUANIDINE NITRATE IN THE RATIO OF ABOUT 72.5 PARTSHYDRAXINE AND ABOUT 27.5 PARTS GUANIDINE NITRATE.